Answer:
ΔU = -70 J
Explanation:
ΔU = Q − W
where ΔU is the change in internal energy,
Q is the heat absorbed by the system,
and W is the work done by the system (on the surroundings).
30 J of thermal energy is released, so Q = -30 J.
40 J of work is done by the system, so W = 40 J.
Therefore, the change in internal energy is:
ΔU = -30 J − 40 J
ΔU = -70 J
